drm/i915: Sanity check the vma->node prior to binding into the GTT

We rely on the VMA being allocated inside the drm_mm and for its allotted
node being large enough to accommodate all the vma->pages.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Matthew Auld <matthew.william.auld@gmail.com>
Reviewed-by: Matthew Auld <matthew.william.auld@gmail.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170225181122.4788-3-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_vma.c

@@ -241,7 +241,15 @@ int i915_vma_bind(struct i915_vma *vma, enum i915_cache_level cache_level,
 	u32 vma_flags;
 	int ret;
 
-	if (WARN_ON(flags == 0))
+	GEM_BUG_ON(!drm_mm_node_allocated(&vma->node));
+	GEM_BUG_ON(vma->size > vma->node.size);
+
+	if (GEM_WARN_ON(range_overflows(vma->node.start,
+					vma->node.size,
+					vma->vm->total)))
+		return -ENODEV;
+
+	if (GEM_WARN_ON(!flags))
 		return -EINVAL;
 
 	bind_flags = 0;
@@ -258,11 +266,6 @@ int i915_vma_bind(struct i915_vma *vma, enum i915_cache_level cache_level,
 	if (bind_flags == 0)
 		return 0;
 
-	if (GEM_WARN_ON(range_overflows(vma->node.start,
-					vma->node.size,
-					vma->vm->total)))
-		return -ENODEV;
-
 	trace_i915_vma_bind(vma, bind_flags);
 	ret = vma->vm->bind_vma(vma, cache_level, bind_flags);
 	if (ret)